Variable speed transmissions are used to transmit power at selectively variable ratios. One class of variable speed transmission includes an inner rotatable member and an outer rotatable member drivingly coupled by a drive element. Rotation of one of the rotatable members drives the other rotatable member through the drive element.
Some prior art variable speed transmissions of this type are very complex as evidenced by Herman U.S. Pat. No. 1,807,035. Others use a complex arrangement of planatary gears as evidenced by Green U.S. Pat. No. 741,904 and Hayden U.S. Pat. No. 977,449.
In the variable speed transmission disclosed in Mitchell U.S. Pat. No. 736,129, ratio change is obtained by displacing the inner rotatable member linearly relative to the outer rotatable member. This changes the radial spacing between the axes of rotation of the inner and outer rotatable members to in turn change the ratio. Although radially displacing the axes of rotation is a desirable way to obtain ratio change, relative linear movement of the rotatable members is not desirable for all applications.
The variable speed transmission of the Mitchell patent used one-way clutches around the periphery of the outer rotatable member to form a driving connection between the drive element and the outer rotatable member. The use of the one-way clutches at the periphery of the outer member is fraught with disadvantages. For example, under high speed operation, centrifugal force would act on the one-way clutches and push them against the outer rotatable member to create relatively high friction. This type of one-way clutch tends to collect grit which in turn causes friction and high wear.
One way clutches of the type shown in the Mitchell patent require very hard, inflexible surfaces for proper operation. In this prior art construction, the one-way clutches operate in a groove formed at the periphery of the outer rotatable member. A primary problem with this construction is that the walls of the groove must be very rigid and accurately formed in order for the one-way clutches to operate satisfactorily.